oak boards ontop of existing unlevel pine!! help

[garywych]

I have bought 27 sq metres of reclaimed oak boards, t+g. im planning to lay them on top of an existing pine floor that is quite unevel. the degree of canter is about 3 inches from one side of the house to the other. the thing is that the dividing walls are sitting on the existing floor so i do not want to disturb them. what im planning is to remove about 2 inches of pine boards about every 400mm to expose the joists across the whole floor. then lat battons of about 25mm x 25mm onto the joits and pack them underneath where they do not meet due to the joist being loweer at that pint. once i have built this and secured it i intend to lay the oak boards ontop of this structure perpendicular to the existing floor boards. at certain points the new boards will be almost touching the existing pine and at others about 2 inches above the pine. i hope the benefit of doing it like this will mean the new boards are effectively fixed to the joists and that they will be a maximum of 2 inches higher than the existing floor.
Any thoughts on this, or am i making it too difficult.
would it be easier to simply lay this tructure on top of the floor without exposing the joists? help :?